ELLEAnothepiano
Congratulations on your merit at grade 6, that's a fine result especially for a thirteen year-old
I know your dilemma well, as I found myself in exactly the same position with Grade 7 the last time the syllabus changed. I was keen on taking the exam with the 'old' syllabus as I had worked hard on learning the pieces I liked the best, while my teacher suggested I was better off learning three pieces from the 'new' syllabus as well, in case I should be unable to take the exam in the last available period (Spring) or if I failed. As it turned out, it all worked out well and I passed with the old pieces.
But my circumstances are different to yours, in that I do not have SATs, other instrumental exams looming, etc etc etc. Speak to your teacher about your feelings on how things are progressing, then together you can plan out your options.
Just to reiterate Sarah123's point about UCAs points, she is absolutely right - you can only gain 'credit' in terms of UCAS points for the HIGHEST grade (6 and above) which you have passed in each 'subject'. So if you pass Grade 8 piano (which I am sure you will), it makes no difference whether or not you have also passed Grades 6 and/or 7 in piano. The same applies to violin - so a pass at Grade 8 violin counts
in addition to piano in UCAS points terms, but if you have Grade 8 violin, then Grade 6 & 7 violin do not.
In my case, I have grade 8 violin (merit) so I get credit for that, but the fact that I never took grades 6 or 7 makes no difference. However, my grade 8 in piano (if/when I get it...) counts too...
These UCAS points may or may not be accepted by Universities, as Sarah123 said, but I believe they can be accepted at most institutions as a
substitute for A Level Music, if you do not / are not able to take this. Most university music departments will accept applicants, even if they do not have A level Music, if they have passed exams in an instrument/voice and Theory of Music, both at Grade 8, before they start their degree.
Hope that makes it clear as mud
denmark